Recurrent process controller



June 9, 1953 E. H. c. BROWN ETAL 2,641,316

REOURRENT PROCESS CONTROLLER Filed Feb. 27, 1950 5 sheets-sheet 1 EUGENE/r. CI MOWAMIRVM lf/wiz ATTORNEY June 9, 1953 E. H. c. BROWN ET AL 2,641,316

REOURRENT PROCESS CONTROLLER EUGE/V" MC. BROWN s? INVENToRs BY M ATTORNEY June 9, 1953 Filed Feb. 27, 1950 E. H. C. BROWN ET AL RECURRENT PROCESS CONTROLLER TILE/P LIN/7' SDV/TCH 5 Sheets-Sheet 5A EECTm-HE//NAUC RELA Y o- MESSUIENRMSE Snventors (Ittorneg June 9, 1953 E. H. c. BROWN ET AL 2,641,315

l RECURRENT PROCESS CONTROLLER A Filed Feb. 27, 1950 5 Sheets-Sheet 4 A PIL/f 90 Pff R/f 67 9A 9 l? L Riny pesssaifwcass J`95 Gttorneg June 9, 1953 E. H. c. BROWN ET AL 2,641,316

REOURRENT PROCESS CONTROLLER 5 Sheets-Sheet 5 Filed Feb. 27, 195o MA$7`ER PRESSURE @suon/.s

l FROM SUPPL Y PRESSURE Gttorneg the fluid pressure acts on the resolving mechanism.

According to another feature of the present invention, the operation of an intermittently or cyclically operated apparatus is maintained in a predetermined relationship to said variable (whether a direct, a square root, or some other relationship is desired) in spite of the occurrences of ambient conditions tending to change the operation thereof, by a timer in cooperation with a` the cooker is predetermined or set by any desired pneumatic or hydraulic master pressure control v system, in conjunction with an automatic batch weighing scale as above described in which the speed of the hopper conveyor is controlled by the timer of the present invention through any suit- 'able control mechanism. The master control pressure is correlated to the desired rate of operation or flow through the cooker, the flow of liquids to the cooker corresponding to the square root of the master control pressure. In order to proportionately vary the rate of feed of grain by the scale, it is necessary to vary the time between dumps. In the present embodiment the timer which controls the time between dumps is set by the master control pressure applied to the timer through a resolving mechanism to produce a time cycle proportional to the inverse square root of the change of the master control pressure,

f and thus a direct proportional relationship between the grain feed and liquid feed to the cooker is maintained at any value of the master pressure.

The variation in time between dumps is accomplished by changing the speed of the conveyor that removes grain from the hopper. For example, where the conveyor is driven by a constant speed motor through a variable speed drive, the drive may be adjusted by any suitable electrical or electro-pneumatic control operated by the timer. vIn one preferred embodiment this adjustment of the drive is made by an air motor positioned by electric-pneumatic relays operating with an air relay of known construction supplied by the master pressure, so that the pressure supplied to the air motor will be changed by the master pressure, thereby reducing the amount of correcting action required by the timer. However, various other mechanisms and arrangements may be employed to secure the desired correction.

The timer applies the required compensation or correction at each cycle of the scale. For this purpose the timer and scale mechanism are set to begin their operating cycles in synchronism, and a mechanism is provided which applied to the scale an accelerating compensation when the timer completes its cycle ahead of the scale, and a retarding compensation when the scale completes its cycle ahead of the timer. When the grain feed and liquid ow are properly coordinated, the timer cycle and scale cycle end substantially simultaneously. Because of the correcting action of the timer it is not necessary that the speed varying mechanism for the conveyor be inherently designed for correlating the grain flow proportional to the liquid ow, because the action of the timer brings about the proper correlation and also acts to compensate for ambient conditions affecting the rate of grain feed.

The invention will be described in greater detail in connection with the accompanying drawings illustrating a preferred embodiment of the invention by way of example, and wherein:

Figure 1 is a diagrammatic view illustrating an apparatus for carrying out the continuous grain cooking process,

Figure 2 is an elevation of a timer,

Figure 3 is a partly schematic side view of the reversing controller,

Figure 4 is an end view of a detail of Figure 2.

Figure 5 is a fragmentary end view of a detail,

Figure 6 is a diagrammatic view explaining the operation of the timer, scale and conveyor drive and their cooperating electrical and iiuid pressure circuits,

Figures 7, 8 and 9 are wiring diagrams to explain the operation of the invention, and

Figure l0 is a schematic view of the pneumatic control system.

Cooker system Referring to the drawing, Figure 1, there is shown a precooker I supplied with a mixture of ground grain and liquid, e. g. water and stillage. The heated mash is pumped to a continuous cooker 2 by pumps 3 controlled by a level controller (not shown) in the precooker which operates suitable controllers for the pumps. l'I'he cooked grain mash is discharged from the continuous cooker 2 into batch fermenters (not shown). Liquid is supplied to precooker I through conduit 4, the rate of flow of liquid being indicated by any suitable indicating apparatus (not shown). The air motor 5 which controls the rate of flow of liquid is positioned by a flow controller which responds to the master pressure. The master pressure is also applied to a. control air relay 6. The rate of ow of liquid to the precooker can be set at any desired value by setting the master pressure at the corresponding value, the liquid flow rate being proportional to the square root of the master pressure.

Ground grain is supplied to the precooker in a continuous flow by a screw conveyor l, which in turn receives its supply from the hammer mill 8. A receiver 9 (Figures l and '7) on a weighing scale I I is supplied with whole grain, and when receiver 9 is loaded with a predetermined weight of grain, the scale beam drops and the bottom of the receiver opens to discharge the grain into hopper I2, from which a screw conveyor I3 carries away the grain to the hammer mill 8. The discharge of ground grain from the hammer mill into screw conveyor I is substanltially continuous and equal to the feed thereto,

so that the flow of grain to the precooker is in effect, governed by the conveyor I3. Grain will flow from receiver 9 in dumping position only as fast as allowed by depletion of the supply of grain in hopper I2, and the scale beam carrying the receiver will rise for refilling only after 'the batch of grain is completely discharged. from the receiver. Conveyor I3 is driven by a motor I 4 through a variable speed drive mechanism I5 which is varied by means of a lever I6 and air motor I1 so that an increase in air pressure on the air motor increases the speed of the conveyor, and a decrease in air pressure decreases the speed of the conveyor.

`ilow of airfrom or into' thischambcr.

Pneu'n'mz'crv ycontrol system The entire pneumatic system for controlling thefco'ntinuous and intermittent yoperations of lthel process is diagrammatically illustrated in lFigure -10,wherein the air relay 6 is of. known construction. (commerciallyknownA as the ,"S-tandatroPoi the Bailey Meter Company). Air

pressure` incharnber. I9 is lemployed to position in chamberf23 or 24,' and the volume chamber Iuiconnected `to chamber 24 provides an. in.-

creased capacity for this y.clnsm'berso as tofreduce the rate of pressure changein chamber 24upon If .the loadingpressure to chamber24 decreases below vthe spring loading, asfby opening of. bleed valve 25, the exhaust valve 26 in chamber I9 will open tol decrease thepre'ssu-re ltherein an. equal amount, andithis decrease is transmitted'to the air motor I'lto reduce the speed of the conveyor I3. However, this reduction in speed of the lconveyor is not correlated tothe liquid feed to the cooker.

.A similarbut reverse action occurs when valve 2'! opensto' introduce air from a pressure source to increase tha-pressure; inr chamber 2li. Thus, by'varyingithe'pressure inschamb'er 24; the pressure: in :chamber I9. may. be madey to assume lanyI value from zero up to. 'thesupply pressure.

The pressure in chamber I9 is' equal to the sum of `thepressures inl chambers 23 andv 24, less the tensionfon'th'e spring.. Any change in setting off the-master pressure wlllautomaticall-y pro-|- ducea change ln pressureiinchamber i 4which acts'upon the conveyor, but as above pointed out, thechange in speed of the'conveyor is not correlated to the liquidieed tothe cooker,

Assuming the screw'conveyor I'3y were operated at a uniform speed, various ambient conditions such as the variation invlevel of thefgrain in `bin or hopper I2f,'variations in thel size of the vgra-in, or vother conditions encountered in service; -would'vcause a variation in the rate of feed f of thek conveyor. Furthermore, a changein air `pressure in chamberv I9` produced by changing lthe masterpressure to seta different flow'v rate of `liquid `toA the precooker would, if'communicated by air motor. I'I to 'variable drive flfresult in a change in speed of the conveyor I3 in the proper direction but not correlatedto the liquid flow to the precooker; The apparatus for maintaining this required correlation' now kwill be described.

Timer Referring toI Figure 2, a panel carries a bracket 28- upon which a gear wheel tis'suitably mounted for rotation. As illustrated, gear Wheel29 is engagedby a *pinionv 39, driven. by an electric Imotor 3i of any' suitable type, although ity will be understood any desired arrangement can be provided for rotating this wheel 29 from'theimoond arm 3-5- onA the gear wheel cooperates with a stop 36A` on vthev bracket toA limit clockwise rotation ofthe gear'wheel and of arm 33e; The-post fil 6 admitsb'fn 'fine adjustment` vto :coordinate the switch operation with 'the stopposition.:

Al shaft 131 extending. frombellows'` assembly carries a cam member 39 pivoted thereon. A switch housing is adjustably fastened to` the cam member and contains a limit or reversing controller switch 4I (Figure) having a pivoted operating arm 42 carrying a roller43.. Upon pivoting of cam 39 clockwise arm Mis engagedby the switchoperatingv Vroller .43 for 'opening' the switcl'i, the switch-being biased. to closedposition by a spring in known manner. A stop (not shown) may befprovided to limit pivotal movement' of cam' member 39 in counterclockwise direction. Arm Illi'is'swiveled'onr shaft 31 and lhas a slot 45 to vreceive a sliding block. The 'arm lis bent over at Elli to 'receive anadjus'tment screw il engaging the block. An operating rod 48 securedv in the block at one end, vhas it's. op-

posite end secured toa diaphragm'orfbellows '49 in the pressuretight housing 5I, and the pressure on the bellows is varied through an air pressure connection 52J in the housing 'connected to the air line controllingV the liquid for the precooken4 Wheel 29 carries a third' arm 54 having a lcon-- tact roller 55 near its end. The edge 56 of cam member 39 is of a special configuration, therderivation ofwhich will be later described. When the counterclockwise rotation of wheel' 29 carries roller`55 into engagementwith earnedge 55, the cam member 39 and switch-housing thereon are rocked clockwise to bring rollerl 43 against the top edge of arm 44, thereby moving' arm 42v to open the switch 4I. This reverses the timer motor, as will hereinafterappear, and the timer then returns to starting position,

It will be observed that the position of switch engaging stop 44 is variable in responseto the position of rod 48, and the dis-tance between switch engaging stop 44 and switch operating roller 43 varies inversely as the master pressure in bellows 49,'this distance being directly Iproportional or equal to the time. The edge 56 of the cam is formed so that in its various angular posi tions, the distance' which the roller 55 travels from zeroposition to actuate the switch 4I and return to zero position, or the time of such travel, is proportional to the square root of the inverse of the movement of rod 48. The timer cycle thus becomes proportional to 'the sq-uaref root of the inverse pressure, and is therefore directly proportional'to the ilowo'f liquid to the precooker. In addition, in the modification shown, the cam edgen isr formed to compensate forl the angularity of lever 44 at various positions in relation to the vmovement of rod 48, and for thean'gular relation of arm 54 to the caml edge. 56. The shape of cam edge 5B may be computed mathematically, or may be laid out by trial: and error.

Itwill. be understood that by arranging the bellows 49 to increase the distance between stop 44 and roller 43 withr increase in pressure, and properly shaping the timer cam edge 56, the timer cycle may be made directly proportional tothe square root of the pressure. Any desired relation between the timer cycle and thepressure may be provided byv suitably shapingv the cam. Also, if desired', the cam'may be carried on orbe positioned by bellows 49.

Electrical circuits The various electrical circuits and the pneu- 'niatic control system for the conveyor' are 'dia- "numeralsi Figures shows-in full lines, thepo'srtions of the various switches and relays when the timer and scale are ready to start their respective cycles in synchronism. The forward or counterclockwise operating circuit of the timer motor 3| comprises lead 6| connected between main 62 and forward direction selector switch 63, lead 64 from terminal F (forward) to themotor 3|, and common return lead 65 to main 66. The switch 63 is held in contact with terminal F by a direction selector relay or solenoid 61 connected by lead 68 to timer limit switch 4|, and by leads 69, 1| to one terminal DS (direction selector) of a relay selector switch 12. When the scale receiver 9 is in up or filling lposition as shown in Figure 6, its limit switch 13 engages the up terminal U, so that in this position solenoid 61 is energized through the circuit comprising lead 14, switch 13 in the U position, lead 15, switch 12, leads 1|, 69, switch 4| and lead 68, to position switch 63 for energizing the forward operating circuit of motor 3|.

The lling of the scale receiver 9 commences, and the motor 3| starts its forward movement, moving timer limit switch 32 to the C contact as shown in dotted lines in Figure 6. In this position operating relay or solenoid 62 is deenergized by opening of the O contact of switch 32, its circuit comprising lead 16, switch 32 and lead 10. When the scale dumps, the opening of scale contact U does not deenergize the direction selector relay 61, because movement of switch 32 to the C contact closes a holding circuit for solenoid 61, comprising lead 16, switch 32 in the C position, leads 11, 18, timer reverse circuit switch 19 in the H position, leads 8|, 69, switch 4| and lead E8. The timer continues its forward phase until roller 55 engages cam 39 to open switch 4|, as shown in Figure '1, thus opening the holding circuit of solenoid 61 to shift forward switch 63 to the PI (pressure increase) contact, and at the same time moving reverse switch 19 to the R (reverse) contact to close the timer reverse circuit. This reverse circuit comprises lead 16, switch 32 in C position1 leads 11, 18, switch 19 in the R position, and lead 83. and energization of the reverse circuit causes the timer motor to start its return movement toward the zero position. The shifting of switch 19 from the I-I position prevents reenergizing of solenoid 61 when switch 4| closes upon disengagement of roller b 55 from cam 39 on the return phase of the timer. Engagement of the contact D (down) by scale limit switch 13 closes the energizing circuit of solenoid 84 of the relay selector switch positioner, which circuit comprises lead 14, switch 13, lead 85, relay energizing and releasing switch 96 in the RE- (relay energizing) position, and lead 81, This moves switch 12 to engage the SS (speed selector) contact and switch 12 is locked in this position by the mechanical interlock of solenoids 84 and 88. The dropping of the scale beam causes opening of the scale receiver by a suitable tripping device (not shown) and the contents of the receiver flow out as fast as the conveyor I3 removes the grain from the hopper I2, While the scale container is emptying the switch 12 is held againts the contact SS, but because the U contact is open no current iiows across switch 12 by lead 89 to speed selector relay or solenoid 90.

Three conditions of operation are possible: (a.) The timer can complete its cycle before the scale; (b) the timer can complete its cycle after the scale; or (c) the timer and scale may complete their cycles substantially simultaneously. These conditions will be described in the order enumerated.

Timer cycle completed before scale cycle 5 Referring to Figure 9, the timer has completed its cycle and arm 33 has moved switch 32 to the O contact to deenergize the reverse circuit of motor 3|, thereby stopping the motor, and to close the energizing circuit of solenoid 82, to move switch 86 to the contact RR (relay release) and move circuit closing switch 92 to the closed position. With the scale in down position as shown, switch 86 completes the energizing circuit of solenoid 88, comprising lead 14, switch 13, lead 05, switch 86 in the RR position and lead 93, thereby releasing switch 12 to the DS position. That is, switch 12 was held in the SS position for the time interval between dumping of the scale and return of the timer to zero position. An accelerating compensation for the scale cycle now is introduced as follows:

Deenergization of solenoid 61 has placed switch 63 in series with speed selector switch 94 in the PI (pressure increase) position and with circuit completing switch 92 in the PI position, the circuit of the pressure increase accelerating relay 95 is energized through lead 6|, switch 63, lead 96, speed selector switch 94, lead 91, switch 92 in the PI position, and lead 98. This opens valve 21 (Figures 6 and 10) to admit additional air from a pressure source to air motor I1 which operates lever I6 of the variable gear drive |5 to increase the speed of conveyor |3 and thus hasten completion of the scale cycle. Upon completion of the scale cycle, the switch 13 rises to the U position, as shown in dotted lines in Figure 9, to energize the circuit of relay 61 through switches 12 and 4|, whereupon switch 63 moves to the F contact to start the motor 3|. As above described. operation of switch 32 by motor 3| to the C contact opens the circuit of solenoid 82 to allow switch 92 to open and thus deenergize the circuit of the pressure increase relay 95 which closes valve 21. This stops the speed increase correction, and the timer and scale cycles now start in unison as described in connection with Figure 6. The scale dumps and the circuit of solenoid 84 is energized so that switch 12 is locked in the SS position as previously described, The timer then opens switch 4I to commence its reverse phase.

Scale cycle completed before timer cycle Upon rising of the scale to complete its cycle before the timer cycle is completed, the parts are in the positions shown in Figure 8. The engagement of scale contact U by switch 13 closes the energizing circuit of speed selector solenoid 90 comprising lead 14, switch 13, lead 15, switch 12 and lead 89, and places pressure decrease switch 99 in the PD (pressure decrease) position. Relay 90 now is energized by a holding circuit comprising lead 6|, switch 63 in the PI position, lead 96, switch 94 in H position, leads |00, B9 and |0|. The circuit of pressure decrease relay |02 thereupon is closed, this circuit comprising lead 16, switch 32 in the C position, leads 11, |03, switch 99 and lead |04. The pressure decrease relay opens valve (Figures 6 and 10) to bleed air from the line of air motor |1 which thereupon operates lever I6 of the variable gear drive I5 to decrease the speed of conveyor I3. This decreased speed continues until timer motor 3| operates switch 32 to disengage contact C at the end of the timer cycle and open the circuit of relay 61 to stop the timer, and open the energizing circuit of the pressure decrease relay |02.

The operation of switch 32 to the O position energizes the circuit of relay 82 and moves switch 8B to the RR position, the timer in the meantime being stopped. The scale is iilling again, and when the scale dumps the release relay 88 is energized to allow switch l2 to move to the DS position. When the scale rises the relay 61 is energized through switch 'l2 to start the timer on its forward phase. Thus the timer has remained inoperative for one scale cycle, and the starting of the next timer cycle occurs simultaneously with the start of the scale cycle.

If the scale and timer cycles are in synchronism, the timer will end its cycle substantially concurrently with the scale cycle, so that the circuit assumes the position shown in full lines in Figure 6 for starting a new cycle, without operating either electro-pneumatic relay, and no correction is imparted to the scale cycle.

Operation The operation of the whole apparatus now will be reviewed. The master air pressure which xes the rate of flow of liquid to the precooker i acts simultaneously on relay 6 and ybellows 49, and determines the position of arm 64. The cam 39 resolves the angular movement of roller 55 into a relation proportional to the inverse of the square root of the movement oi' arm 44, so that the timer cycle is proportional to the square root of the inverse of the air pressure, and thus is directly proportional to the liquid feed to the precooker i. Should the timer complete its cycle before the scale returns to its up position, the pressure increase electro-pneumatic relay 95 is energized to increase the pressure applied to air motor i7, and movement thereof increases the speed of conveyor I3 which shortens the scale cycle. Upon completion of the scale cycle the correction stops, and the timer and scale `start their cycles in synchronism.

Should the scale cycle be completed before the timer cycle, the timer stops, and the pressure decrease electro-pneurnatic relay HB2 is energized to decrease the pressure applied to air motor I7, and movement thereof decreases the speed of conveyor I3 to lengthen the scale cycle. The rising of the scale stops the correction. The timer remains stopped while the scale receiver fills and dumps, and when the scale again rises, the timer and scale commence their cycles in synchronism.

We claim as our invention:

In combination with a reversible timer, and a cyclically operating apparatus to be controlled: speed control circuits for the apparatus to be controlled having speed increase and speed decrease circuit switches therein; a speed selector relay for selectively operating said switches, one of said switches being common with a holding circuit for the speed selector relay; forward and reverse circuits for said timer including direction selector switches; a direction selector relay for selectively operating said direction selector switches, one of said direction selector switches being common to the holding circuit of the speed selector relay, and the other direction selector switch be ing common to a holding circuit for the direction selector relay; a relay selector switch for energizing the direction selector relay in one position and the speed selector relay in the other position; limit switch means for the cyclically operating apparatus; positioning means for the relay selector switch including relay energizing and relay releasing switch connected with the limit switch means of the apparatus to be controlled when in one position, said limit switch means being connected to the relay selector switch when said apparatus is in another position; a circuit completing switch for one of the speed control circuit switches; a position operating relay for the circuit completing switch and the relay energizing and relay releasing switches; and limit switches operated by the timer, one of said timer limit switches being in the holding circuit of the direction selector relay, and the other timer limit switch being common to the circuit of said position operating relay, the holding circuit of the direction selector relay, one of the speed control switches, and the timer reverse circuit.

EUGENE H. C. BROWN. IRVING LEFKOWITZ.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 2,050,614 Kerr Aug. 11, 1936 2,218,390 Alexander Oct. 15, 1940 2,276,382 Francis Mar. 17, 1942 2,408,221 Michel Sept. 24, 1946 2,414,467 Hunt Jan. 21, 1947 2,449,953 Rippingille Sept. 21, 1948 2,467,181 Barnard et al. Apr. 12, 1949 

